1. Field of the Invention
This invention relates to a back light module of LCD device, and more particularly to a back light module of LCD device using a reflecting plate as a lamp reflector to reflect the light generated by light reflecting generating units and using a metallic material installed on a surface of the reflecting plate and/or a coupling elements to overcome the EMI problem.
2. Description of the Prior Art
A traditional back light module of an LCD (liquid crystal display) device generally comprises a support frame, a light guiding plate, a lamp module, a reflecting plate assembled under the bottom of light guiding plate, and various optical films assembled on the upper of the light guiding plate. The various optical films include a diffusing film, a light condensing film, a light enhancement film, a prism film, and so on. The lamp module includes a U-shaped lamp reflector reflecting the light emitted from the lamp into the light guiding plate. Furthermore, the light guiding plate guides the light to the front LCD device.
In the conventional back light module, the lamp is assembled within the U-shaped lamp reflector. Nevertheless, there are commonly matching problems occurred among the U-shaped lamp reflector, the light guiding plate, and the reflecting plate, in practice. These matching problems always cause the effects of dark region, light leakage, dark stripe, and wrinkling in some areas of the back light module. Moreover, the U-shaped lamp reflector is generally made of metallic materials and harder than the light guiding plate, and therefore the light guiding plate is scraped easily to generate dust during assembly or re-module processing.
In the conventional arts, the lamp module of the back light module is supported by a plastic frame (i.e., support frame) which is fixed by screws in back light module assembly process. However, the plastic frame will deform and oppress the lamp when the assembling screws are turned to tighten them. This causes the lamp bent and dark regions, so the displaying quality will reduce.
Furthermore, the lamp reflector of the lamp module and the reflecting plate compress each other easily, so the wrinkling phenomenon will occur in the reflecting plate.
Besides, the lamp reflector, the light guiding plate, and the reflecting plate are tightly connected with each other. While the LCD device composed of the back light module and the LCD panel processes with shock test, the lamp reflector compresses the light guiding plate and the reflecting plate, and therefore the drop test is failure. Namely, the structure mentioned above results in that toleration for collision or dropping goes down. Therefore, the displaying quality is reduced, and even the LCD penal can not further use due to some external forces under general collisions.
Hence, people familiar with those skills in the art tried to fabricate a back light module without the lamp reflector for LCD device. For example, US Patent No. US2003/0043314A1 discloses a back light module without U-shaped lamp reflector. However, the back light module mentioned above uses circle-shaped lamp, not linear-shaped light generating unit. Moreover, the back light module uses a reflecting plate to cover the lamp for replacing the lamp reflector in the conventional arts. However, the conventional lamp reflector is made of metal to avoid electro-magnetic interference (EMI) problem for eliminating interference in image quality. Accordingly, the LCD device without lamp reflector causes electro-magnetic interference (EMI) problem. Furthermore, the wrinkle of the reflecting plate resulted from temperature variability still exits in the patent.
Besides, U.S. patent application Ser. No. 2002/0021383A1 discloses a structure of back light module. A reflecting plate is banded upward to form an upper plate for avoiding the problems of light leakage and wrinkle. Similarly, this patent application still does not use conventional metal lamp reflector and has the electromagnetic interference.
In accordance with problems mentioned above, the inventor have researched extensively in the back light module of LCD device and then completed the present invention.